The present invention relates to a fluidic device, a fluidic module, and a method of handling a liquid, which are suited in particular to fill a fluid chamber that is closed with the exception of a fluidic access with liquid.
In centrifugal microfluidics, the centripetal acceleration of a disk under rotation is used to transport and control liquid amounts in the nanoliter to milliliter range in controlled manner. The liquid transport usually is done in channels on the disk having characteristic dimensions in the micrometer to millimeter range.
Examples of such microfluidic platforms are described in S. Haeberle and R. Zengerle, “Microfluidic Platforms for Lab-on-a-Chip Applications”, Lab Chip, p. 1094-1110, 2007; J. V. Zoval et al., “Centrifuge-based fluidic platforms”, Proceedings of the IEEE, Vol. 92, No. 1, p. 140-153, January 2004; J. Ducrée et al., “The centrifugal microfluidic Bio-Disk platform”, Journal of Micromechanics and Microengineering, Vol. 17, No. 7, p. S103-S115, 2007; and M. Madou et al., “Lab on a CD”, Annual Review of Biomedical Engineering, Vol. 8, p. 601-628, 2006.
Typical applications of centrifugal microfluidics are in the life sciences and in medical diagnostics. Advantages of the centrifugal microfluidics are based on the improved integration, automation, miniaturization and parallelization of process flows by means of application-specific cartridges that may be played in a multi-purpose device in the ideal case. Many methods may necessitate switching, dosing and distributing a sample, the so-called aliquoting, for subsequently performing some parallel experimentation steps. After the aliquoting, the sample then reacts with reagents specifically provided in the respective channels, in many applications.
Aliquoting of partial samples by combination of hydrophilic channels with hydrophobic zones is described in WO-A1-2004/083108. Aliquoting via a centrifugally filled distribution channel is described in U.S. Pat. No. B2-6,752,961. The dosed volume here substantially corresponds to the geometry of a certain structural portion. Here, reliable division into partial volumes defined independently of the volumes of the substances provided in channel portions after the dividing structure is desirable. Moreover, the liquids in the reaction chambers should be separated in fluidically clean manner after the splitting in order to avoid penetration of the upstream substances into other reaction chambers.
For controlling processes on a disk, up to now there are several possibilities to stop or let liquids pass again at controlled points and at controlled times. One example is generating a local hydrophobization with or without simultaneous shrinkage of the channel width, as described in M. Madou et al., “Lab on a CD”, Annual Review of Biomedical Engineering, Vol. 8, p. 601-628, 2006. In this method, the flow is counteracted by a flow barrier caused via the interfacial tension and only exceeded starting at a certain centrifugal acceleration. A further possibility for stopping liquids is an abrupt and sharp-edged channel expansion in a hydrophilic channel, at it is described in D. C. Duffy et al., “Microfabricated centrifugal microfluidic systems: Characterization and multiple enzymatic assays”, Analytical Chemistry, Vol. 71, No. 20, p. 4669-4678, October 1999. Here, a resistance, which again is overcome only starting at a certain rotational frequency, is presented to the further flow by the superficial tension of the water.
Another known possibility of temporarily stopping liquids are siphon structures, for example see C. T. Schembri et al., “Centrifugation and Capillarity Integrated Into A Multiple Analyte Whole-Blood Analyzer”, Journal of Automatic Chemistry, Vol. 17, No. 3, p. 99-104, May 1995. Here, at first capillary filling of a siphon-shaped structure is suppressed by an adverse centrifugal field. If the rotational frequency drops below a certain threshold, the siphon is filled capillarily, and the leading meniscus may sink radially outside the liquid level in the upstream reservoir. A higher rotational speed then subsequently conveys the liquid further. The siphon additionally may be filled by the inlet-side addition of a displacement volume.
Apart from the basically reusable valves mentioned, there also exist so-called sacrificial valves, which cannot be used again after a single actuation. One example of such valves is barriers of wax or thin foils in the flow channel, which are melted by a laser and thus allow for the flow. In this respect, reference can be made, for example, to Y. K. Cho et al., “One-step pathogen specific DNA extraction from whole blood on a centrifugal microfluidic device”, Lab on a Chip, Vol. 7, No. 5, p. 565-573, February 2007.